In my experience a fully charged 2500mah battery (like the one of the LG L7II) will last long enough for hikes etc.

An exchangeable battery is not necessarily needed, but desired, since somtimes there is only limited access to electricity and time to charge the mobile fully.

Single hand usage

Limits mobile size to a maximum of ca. 4.7”

SD card slot

A must to have enough memory for photos, videos and open street maps.

Quick reliable GPS

Good startup time

Robustness under hiking conditions

Good camera

Good contrast and sharpness

Good low-light capabilities

Fast trigger

LCD

Readable in sun light

Preferably HD resolution

Not necessarily Full HD

Comparison table of smartphones fulfilling the above conditions - listed are Android smartphones with a small form factor and an SD Card slot:

Model

Size

GPS

Cam

Battery

Exchangeable Battery

LCD/Brightness

Other

Price (09/2014)

Samsung S3 neo+

4.8”

++

+

++

yes

+

+Kitkat 4.4.2 -size

210 EUR

Samsung S3

4.8”

++

+

++

yes

+

−1GB RAM +Bluetooth -size

240 EUR

Htc One mini II

4.5”

++

+

++

no

++

390 EUR

Samsung S4 mini

4.3”

++

+

+

yes

o

-led -flash

240 EUR

LG L7II

4.3”

o

+

++

yes

o

+price -average gps

120 EUR

LG L9II

4.7”

o

o

++

yes

+

+price -average cam and gps

140 EUR

Huawei P7 mini

4.5”

+

o

+

no

+

-average cam

220 EUR

Samsung S4 9515

4.8”

++

++

++

yes

++

-size -low-light

340 EUR

LG G3 s

5.0”

++

+

++

yes

++

-too big -back buttons

290 EUR

Samsung S5 mini

4.5”

+

+

+

yes

+

+waterproof -blurry cam under low light

360 EUR

Sony Z1 compact

4.3”

++

-

++

no

++

+waterproof -unsharp 8MP cam auto mode

330 EUR

Sony Z3 compact

4.6”

++

-

++

yes

++

+waterproof -unsharp 8MP cam auto mode

500 EUR

A “mini” model with excellent camera, fast GPS, SD-card slot and a long run time appears to be pretty hard to find. Interestingly, the “not-so-mini” S3 has been updated with a new Android version called “S3 neo” and it is just a tad bigger than 4.7”.

So it is a shoot-out between the Samsung S3 neo, the S4 mini and the HTC One mini II.

On the down-side the S3 neo is a tad too big to be considered a single-hand mobile, but it is still usable with apps that do not have important ui elements in the top left corner. On the up-side, the S3 neo has got a couple of features (quad core, good display, led, flash, exchangeable battery) its competitors are missing even at a higher price point.

So for the price of 210 EUR the Samsung S3 neo wins!!! Followed by the HTC One mini II and the Samsung S4 mini. The latter are a good options for those folks who like to get a smaller mobile or who do not like the S3 plastic (I do not care much, because for hiking purposes my mobile gets a mumbi silicon case (transparent black) and a display protector, anyways).

The LG L9II and the LG L7II are still a steal for those who are looking below the 200 EUR price point.

The Samsung S4 is about the same size as the S3, has a better cam but is very noisy in low-light conditions (tested hands-on) and is priced above 300 EUR.

Here are a couple of smartphones, which do not meet above small-form-factor requirement, but are interesting as well:

Model

Size

GPS

Cam

Battery

Exchangeable Battery

SD-Card

LCD/Brightness

Other

Price (11/2014)

Samsung S5

5.1”

++

+++

++

yes

yes

++

+best cam +waterproof

440 EUR

Samsung K Zoom

4.8”

+

++

++

yes

yes

+

+zoom -unsharp border

340 EUR

Huawei P8 Lite

5”

+

++

++

no

yes

+

+good package for the money

250 EUR

Samsung Note 4

5.7”

++

+++

++

yes

yes

++

--expensive -waterproof

600 EUR

Huawei Mate 7

6”

+

++

+++

yes

yes

++

+good alternative to note 4 -waterproof

400 EUR

LG G3

5.5”

+

++

++

yes

yes

++

-back buttons

440 EUR

Google Nexus 5

4.9”

+

+

+

no

no

+

-low light

340 EUR

Google Nexus 6

6”

+

++

++

no

no

++

-huge --expensive

650 EUR

Huawei P8

5.2”

+

++

++

no

yes

++

+waterproof

500 EUR

Huawei G7

5.5”

+

+

++

no

yes

+

260 EUR

Motorola Moto X

4.7”

+

o

++

no

no

+

300 EUR

Motorola Moto X II

5.2”

+

++

+

no

no

++

-expensive

500 EUR

Huawei P7

5”

+

++

o

no

yes

++

-flash light

260 EUR

Sony Z2

5.2”

+

+

+

no

yes

++

-unsharp noisy cam

380 EUR

Sony Z3

5.2”

+

+

+

no

yes

++

-noisy cam

500 EUR

Priced at 440 EUR, the Samsung S5 has the best mobile cam (tested hands-on, also see this dpreview test) and gps/outdoor package on the market today, but due to its size it is not suited very well for single-hand usage.

Notes on camera performance: If have been testing the camera of most of the above models by myself. In a direct comparison the cameras quickly show their weaknesses. For example, the lack of sharpness of the Sony camera modules is just so evident in a direct comparison to the Samsung S5 I am wondering why all tests speak of excellent Sony Z1/2/3 cameras. Of course in bright outdoor conditions the differences are less evident, but if you just shoot a couple of indoor pictures under not-so-bad-but-still-demanding lighting conditions, the competition can be quickly sorted out into the good and the bad guys.

Notes on battery performance: External usb battery packs now ship for about 15 EUR (at 6000mah capacity). On a longer hiking or camping tour I recommend taking one of those with you, since it is sometimes difficult to get access to an outlet. In that case, having 6000mah of additional power will allow to to recharge your mobile and keep it running for about 3–4 days. This lowers the importance of an exchangeable battery.

The final buying recommendation:

The buying matrix leaves me with no substantial clue so far (12/2014), which phone to buy right now. If the main priority were a decent cam, gps and run time, I’d buy the Samsung S5 right away. But it is still expensive and too large for my liking. The same holds for the Samsung Note 4, which has an excellent cam, but is even more pricey. Maybe I just wait until the S5 gets cheaper after MWC in March 2015 and see if I can get accustomed to its size.

Development Impact:

As a result of the lack of a small-size mobile with a decent cam, I am going to design all my apps in a way so that they are still usable by thumb only even for large mobile touch screens. This is achieved by not placing important ui elements in the top-left corner.

So a good ui design principle for outdoor usage is to place all important elements near the bottom. The ping app is already designed that way: For this particular app it is most important to change from tab to tab and start and stop the main activities (gps, cam and transmission). Changing the tab is achieved by swiping with the thumb. Starting and stopping activities is achieved by buttons that are placed on the bottom of each tab.

MWC March, 1st 2015:

After the presentation of the Samsung S6 and the S6 Edge on the MWC 2015, it is clear that the S6 is an excellent mobile with an even better camera than the S5, but it is not a good phone for hiking purposes i.m.h.o.

In comparison to the S5, it lacks the presence of an SD card slot, it does not have an exchangeable battery anymore and it is not water-resistant anymore. At an initial price point of 700 EUR it does not compare very well against the S5.

But I didn’t expect the S6 to be a competitor for the S5, I did expect the prices for the S5 to plunge after the presentation of the S6. Indeed, prices have dropped from around 430 EUR to already 390 EUR. If the price comes down to 350 EUR, I am going to order my S5…

Update April, 28th 2015:

The Samsung S5 revision with LTE+ and a faster processor (Snapdragon 805 instead of 801) is becoming available. Its model number is G901F instead of G900F.

Camera- and memory-wise it is basically all the same, except that it is reported to be 20% faster (and offers LTE+ off course, but I for myself cannot make use of the improved download speed, since I am using HSDPA most of the time). Sales price is about 50 EUR higher than the regular price.

Sounds good overall, but if someone wants to flash Cyanogenmod instead of the stock Samsung Android rom, one should better stick with the regular S5. CM12 is not [yet] as stable for the G901F as for the G900F.